Ultraviolet and vacuum ultraviolet antireflection substrate

ABSTRACT

An antireflection substrate comprising a substrate which is transparent to ultraviolet and vacuum ultraviolet rays in the wavelength region from 155 nm to 200 nm and a mono-, bi- or tri-layer antireflection film formed on at least one side of the substrate, wherein the refractive index and the physical thickness of the antireflection film at the center wavelength λ 0  of the wavelength region of ultraviolet or vacuum ultraviolet light which needs antireflection satisfy particular conditions, and an optical component for a semiconductor manufacturing apparatus and a substrate for a low-reflection pellicle which is the ultraviolet and vacuum ultraviolet antireflection substrate

TECHNICAL FIELD

[0001] The present invention relates to an ultraviolet and vacuumultraviolet antireflection substrate. In particular, it relates to anantireflection substrate suitable for various low-reflection lenses,substrates of low-reflection photomasks and substrates of low-reflectionpellicles (pellicle membranes) used in exposure to light in theultraviolet and vacuum ultraviolet regions in manufacture ofsemiconductor integrated circuits.

BACKGROUND ART

[0002] In recent years, the resolution of exposure systems forfabrication of semiconductor integrated circuits is increasing in orderto improve the integration of semiconductor circuits. Exposure lighthaving shorter wavelengths is increasingly used to improve theresolution of exposure systems, and exposure light has changed fromg-line (wavelength: 435 nm) to i-line (wavelength: 365 nm) and then toKrF excimer laser beams (wavelength: 248 nm) in current use. Even ArFexcimer laser beams (wavelength: 193 nm) and F₂ laser beams (wavelength:157 nm) in the vacuum ultraviolet region are being put into practicaluse.

[0003] These exposure systems use optical materials such as lenses,photomasks and pellicles, which serve as dust covers for photomasks. Afamiliar material for lenses and photomasks is synthetic quartz glass,while synthetic quartz glass and transparent fluoroplastics are known asmaterials for pellicle membranes.

[0004] However, the refractive indices of such materials as syntheticquartz glass and transparent fluoroplastics increase as the wavelengthof the exposure light becomes shorter, and therefore, if nothing isdone, the light loss resulting from surface reflection and thedevelopment of flare ghosts are prominent. There is another problem thatthe high light transmission, for example, of at least 95%, required inthe ultraviolet region and the vacuum ultraviolet region is not secured.

[0005] Therefore, the first object of the present invention is toprovide an antireflection substrate which suppresses light lossresulting from surface reflection and development of flare ghosts in theultraviolet region and the vacuum ultraviolet region.

[0006] The second object of the present invention is to provide anantireflection substrate having high light transmission.

DISCLOSURE OF THE INVENTION

[0007] The present invention provides an ultraviolet and vacuumultraviolet antireflection substrate (hereinafter referred to as “thefirst substrate”) comprising a substrate which is transparent toultraviolet and vacuum ultraviolet rays in the wavelength region from155 nm to 200 nm and a monolayer antireflection film formed on at leastone side of the substrate, wherein the center wavelength λ₀ of thewavelength region of ultraviolet or vacuum ultraviolet light which needsantireflection, the refractive index n_(s) of the substrate at thewavelength of λ₀, the refractive index n₁ of the antireflection film atthe wavelength of λ₀ and the physical thickness d₁ of the antireflectionfilm satisfy the conditions that n₁<n_(s), and that n₁d₁ is almost(¼+m/2)λ₀ (wherein m is an integer of at least 0).

[0008] In the present invention, n₁d₁ being almost (¼+m/2)λ₀ (m is aninteger of at least 0) means that (0.187+m/2)λ₀≦n₁d₁≦(0.327+m/2)λ₀.

[0009] The present invention also provides an ultraviolet and vacuumultraviolet antireflection substrate (hereinafter referred to as “thesecond substrate”) comprising a substrate which is transparent toultraviolet and vacuum ultraviolet rays in the wavelength region from155 nm to 200 nm and a bilayer antireflection film comprising a secondlayer and a first layer formed on at least one side of the substrate inthis order from the substrate side, wherein the center wavelength λ₀ ofthe wavelength region of ultraviolet or vacuum ultraviolet light whichneeds antireflection, the refractive index n_(s) of the substrate at thewavelength of λ₀, the refractive index n₂ of the second layer at thewavelength of λ₀, the physical thickness d₂ of the second layer, therefractive index n₁ of the first layer at the wavelength of λ₀, and thephysical thickness d₁ of the first layer satisfy the conditions thatn₁<n_(s)<n₂, that n₁d₁ is almost (¼+m/2)λ₀ (wherein m is an integer ofat least 0), and that 0.05λ₀≦n₂d₂≦0.50λ₀.

[0010] The present invention further provides an ultraviolet and vacuumultraviolet antireflection substrate (hereinafter referred to as “thethird substrate”) comprising a substrate which is transparent toultraviolet and vacuum ultraviolet rays in the wavelength region from155 nm to 200 nm and a trilayer antireflection film comprising a thirdlayer, a second layer and a first layer formed on at least one side ofthe substrate in this order from the substrate side, wherein the centerwavelength λ₀ of the wavelength region of ultraviolet or vacuumultraviolet light which needs antireflection, the refractive index n_(s)of the substrate at the wavelength of λ₀, the refractive index n₃ of thethird layer at the wavelength of λ₀, the physical thickness d₃ of thethird layer, the refractive index n₂ of the second layer at thewavelength of λ₀, the physical thickness d₂ of the second layer, therefractive index n₁ of the first layer at the wavelength of λ₀, and thephysical thickness d₁ of the first layer satisfy the followingconditions (1) to (4):

n ₁ , n ₃ <n _(s) and n ₁ , n ₃ <n ₂,  (1)

0<n ₁ d ₁≦0.47λ₀,  (2)

0.14λ₀ ≦n ₃ d ₃≦0.33λ₀,  (3)

[0011] and

0.16λ₀ ≦n ₂ d ₂≦0.38λ₀,  (4)

0.64λ₀ ≦n ₂ d ₂≦0.86λ₀, or

1.13λ₀ ≦n ₂ d ₂≦1.35λ₀

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a schematic sectional view of the first substrate of thepresent invention.

[0013]FIG. 2 is a schematic sectional view of the second substrate ofthe present invention.

[0014]FIG. 3 is a schematic sectional view of the third substrate of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] Specific Embodiments are described below.

[0016] The antireflection film of the first substrate, or the film incontact with the substrate, is preferably made of at least one speciesselected from the group consisting of MgF₂, AlF₂, BaF₂, LiF, SrF₂,Na₃AlF₆, NaAlF₂ and CaF₂. Especially, it is preferred to be a layer madeof at least one species selected from the group consisting of MgF₂ andCaF₂.

[0017] Each layer in the antireflection film of the second substrate isa layer made of at least one species selected from the group consistingof MgF₂, AlF₂, BaF₂, LiF, SrF₂, Na₃AlF₆, NaAlF₂, CaF₂, LaF₂, PbF₂, YF₃,SiO₂, Al₂O₃ and HfO₂. More specifically, the layer closer to thesubstrate (the second layer) is the same as the above-mentionedantireflection film of the first substrate, and the upper layer (thefirst layer) is made of at least one species selected from LaF₂, PbF₂,YF₃, SiO₂, Al₂O₃ and HfO₂. Each layer in the antireflection film of thesecond substrate is preferably made of at least one species selectedfrom MgF₂, CaF₂, SiO₂, Al₂O₃ and HfO₂.

[0018] Each layer in the antireflection film of the third substrate is alayer made of at least one species selected from the group consisting ofMgF₂, AlF₂, BaF₂, LiF, SrF₂, Na₃AlF₆, NaAlF₂, CaF₂, LaF₂, PbF₂, YF₃,SiO₂, Al₂O₃ and HfO₂. More specifically, the two layers closer to thesubstrate are the same as the above-mentioned antireflection film of thesecond substrate, and the outermost layer is a layer made of at leastone species selected from MgF₂, AlF₂, BaF₂, LiF, SrF₂, Na₃AlF₆, NaAlF₂,CaF₂ and SiO₂. Each layer in the antireflection film of the thirdsubstrate is preferably made of at least one species selected from MgF₂,CaF₂, SiO₂, Al₂O₃ and HfO₂.

[0019] In view of control of the absorption of light at wavelengths from150 to 200 nm, the antireflection film is made of at least one speciesselected from MgF₂, CaF₂, Na₃AlF₆, YF₃, PbF₂ and SiO₂.

[0020] In the present invention, the center wavelength λ₀ of thewavelength region of the ultraviolet or vacuum ultraviolet light whichneeds antireflection (hereinafter referred to as “the antireflectioncenter wavelength”) means the wavelength of the exposure light in theultraviolet or vacuum ultraviolet region to be transmitted through anoptical component using the antireflection substrate, and variesdepending on the exposure light.

[0021] The antireflection center wavelength λ₀ is a wavelength from 150nm to 250 nm, preferably from 150 nm to 200 nm. As λ₀, 157 nm or 193 nmmay be mentioned. An antireflection substrate wherein λ₀ is 193 nmcontrols reflection of ArF excimer laser beams (wavelength: 193 nm) mosteffectively. An antireflection substrate wherein λ₀ is 157 nm controlsreflection of F₂ laser beams (wavelength: 157 nm) most effectively.

[0022] The antireflection substrate of the present invention preferablyhas a light transmittance of at least 90% at the antireflection centerwavelength λ₀ of the antireflection substrate of the present inventionin order to secure good pattern transfer in the lithography step, whenused as an optical component for a semiconductor manufacturingapparatus. The light transmittance is preferably at least 95%, morepreferably at least 96%, in particular at least 98%.

[0023] The antireflection substrate of the present invention preferablyuses, as the substrate, a synthetic quartz glass or a transparentfluoroplastic which is transparent to ultraviolet and vacuum ultravioletrays in the wavelength region from 155 nm to 200 nm, particularly from155 nm to 250 nm. In the present invention, transparent, when referredto for a synthetic quartz glass, means that the internal transmittancein the ultraviolet and vacuum ultraviolet wavelength regions of from 155nm to 200 nm is at least 50%, preferably at least 70%, more preferablyat least 80%, particularly preferably 95%. When referred to for atransparent fluoroplastic, for example, having a cyclic structure on themain chain, transparent means that the internal transmittance in theultraviolet and vacuum ultraviolet wavelength regions of from 150 nm to200 nm, particularly from 150 nm to 250 nm is at least 80%, preferablyat least 90%, more preferably at least 95%.

[0024] In the present invention, the substrate is preferably made of asynthetic quartz glass doped with at least 1 ppm (particularly at least10 ppm, more preferably at least 100 ppm) of fluorine in view of thelaser beam resistance.

[0025] When the substrate is made of a synthetic quartz glass doped withat least 1 ppm of fluorine, use of a layer made of a fluoride as thelayer in contact with the substrate secures good adhesion to thesubstrate and allows provision of an antireflection substrate havingprominent laser beam resistance attributable to the substrate.

[0026] In the first to third substrates, the antireflection film isformed at least one side of the substrate and may be formed on the bothsides of the substrate or only one side of the substrate. When the firstto third substrates have antireflection films on both sides of thesubstrate, the two films on the opposite two sides may be different inconstituent and physical thickness.

[0027] The layer in the first to third substrates which in contact withthe substrate (namely, the antireflection film in the first substrate,the second layer in the second substrate or the third layer in the thirdsubstrate) and the outermost layer in the second or third substrate(namely, the first layer) are preferably made of CaF₂ and/or MgF₂ inview of durability. Layers made of MgF₂ are more preferable to attainlow refractive index and better antireflection.

[0028] The second layer in the antireflection film of the thirdsubstrate is preferably a layer made of SiO₂ and/or CaF₂, having a smallabsorption coefficient. Particularly preferred is SiO₂ to give anantireflection film with good abrasion resistance. A small amount of Al,B, P or the like may be so incorporated in SiO₂ as not to ruin theeffects of the present invention.

[0029]FIG. 1 shows an embodiment of the first substrate which comprisesa substrate 1 and monolayer antireflection films 2 a and 2 b on bothsides of the substrate 1. When the antireflection center wavelength λ₀,the refractive index n_(s) of the substrate 1 at the wavelength of λ₀,the refractive indices n_(1a) and n_(1b) of the antireflection films 2 aand 2 b at the wavelength of λ₀ and the physical thicknesses d_(1a) andd_(1b) of the antireflection films 2 a and 2 b satisfy the conditionsthat n_(1a), n_(1b)<n_(s), and that n_(1a)d_(1a) and n_(1b)d_(1b) arealmost (¼+m/2)λ₀ (wherein m is an integer of at least 0), an ultravioletand vacuum ultraviolet antireflection substrate having a reflectance(the degree of reflection from one side at the antireflection centerwavelength λ₀) of at most 3%, preferably at most 2% around thewavelength λ₀ can be obtained.

[0030]FIG. 2 shows an embodiment of the second substrate which comprisesa substrate 1 and bilayer antireflection films 3 and 4 formed on bothsides of the substrate, each comprising a second layer 3 a or 3 b and afirst layer 4 a or 4 b formed in this order from the substrate side.When the antireflection center wavelength λ₀, the refractive index n_(s)of the substrate 1 at the wavelength of λ₀, the refractive indicesn_(2a) and n_(2b) of the second layers 3 a and 3 b at the wavelength ofλ₀, the physical thicknesses d_(2a) and d_(2b) of the second layers 3 aand 3 b, the refractive indices n_(1a) and n_(1b) of the first layers 4a and 4 b at the wavelength of λ₀, and the physical thicknesses d_(1a)and d_(1b) of the first layers 4 a and 4 b satisfy the conditions thatn_(1a)<n_(s)<n_(2a) and n_(1b)<n_(s)<n_(2b), that n_(1a)d_(1a) andn_(1b)d_(1b) are almost (¼+m/2)λ₀ (wherein m is an integer of at least0) and that 0.05λ₀≦n_(2a)d_(2a)≦0.50λ₀ and 0.05λ₀ ≦n_(2b)d_(2b)≦0.50λ₀,an ultraviolet and vacuum ultraviolet antireflection substrate having areflectance (the degree of reflection from one side at theantireflection center wavelength λ₀) of at most 3%, preferably at most2% around the wavelength λ₀ can be obtained.

[0031]FIG. 3 shows an embodiment of the third substrate which comprisesa substrate 1 and trilayer antireflection films formed on both sides ofthe substrate 1, each comprising a third layer 5 a or 5 b, a secondlayer 6 a or 6 b and a first layer 7 a or 7 b formed in this order fromthe substrate side. When the antireflection center wavelength λ₀, therefractive index n_(s) of the substrate 1 at the wavelength of λ₀, therefractive indices n_(3a) and n_(3b) of the third layers at thewavelength of λ₀, the physical thicknesses d_(3a) and d_(3b) of thethird layers, the refractive indices n_(2a) and n_(2b) of the secondlayers at the wavelength of λ₀, the physical thicknesses d_(2a) andd_(2b) of the second layers, the refractive indices n_(1a) and n_(1b) ofthe first layers at the wavelength of λ₀, and the physical thicknessesd_(1a) and d_(1b) of the first layers satisfy the following conditions(1) to (4) concerning n_(3a), d_(3a), n_(2a) d_(2a), n_(1a) and d_(1a)and similar conditions concerning n_(3b), d_(3b), n_(2b) d_(2b), n_(1b)and d_(1b), an ultraviolet and vacuum ultraviolet antireflectionsubstrate having a reflectance (the degree of reflection from one sideat the antireflection center wavelength λ₀) of at most 3%, preferably atmost 2% around the wavelength λ₀ can be obtained:

n _(1a) , n _(3a) <n _(s) and n _(1a) , n _(3a) <n _(2a),  (1)

0<n _(1a) d _(1a)≦0.47λ₀,  (2)

0.14λ₀ ≦n _(3a) d _(3a)≦0.33λ₀,  (3)

[0032] and

0.16λ₀ ≦n _(2a) d _(2a)≦0.38λ₀,  (4)

0.64λ₀ ≦n _(2a) d _(2a)≦0.86λ₀, or

1.13λ₀ ≦n _(2a) d _(2a)≦1.35λ₀.

[0033] In the present invention, the total physical thickness of theantireflection film is preferably at most 150 nm. When antireflectionfilms are formed on both sides of the substrate, the total physicalthickness of each antireflection film is preferably at most 150 nm.

[0034] The upper limit of 150 nm which inevitably imposes a limitationon the thickness of each layer, leads to control of contamination of thelayers, and as a result, contributes to improvement of thetransmittance. The upper limit of 150 nm which inevitably imposes alimitation on the thickness of each layer, leads to control of thesurface roughness of each layer while it is being formed (by vapordeposition or the like), and as a result, contributes to control ofreflection and the smoothness of the antireflection film (as isdescribed later).

[0035] The upper limit of 150 nm makes it possible to control doublerefraction (as is described later) while keeping the surface tension ofthe antireflection film low.

[0036] It is advantageous to appropriately select the layer structure ofthe antireflection film, the refractive index of each layer and thephysical thickness of each layer so that the reflectance around thewavelength of 632.8 nm is at most 3.5%, because the alignment of anexposure system using a He—Ne laser becomes easy.

[0037] In the present invention, the difference between the maximum andthe minimum of the transmission of light at the antireflection centerwavelength λ₀ by the antireflection substrate is preferably at most 1%.If the difference between the maximum and the minimum of the lighttransmission exceeds 1%, the antireflection substrate, when used as asubstrate of a low-reflection pellicle, refracts the light path and canlead to displaced pattern transfer onto a wafer. It is particularlypreferable that the difference between the maximum and the minimum ofthe light transmission is at most 0.5%.

[0038] In order to attain good pattern transfer in the lithography step,it is preferred that the light transmittance of the pellicle membrane isat least 90%, and the difference in the light transmittance over theentire surface of the pellicle membrane is at most 1%. “The differencein the light transmittance” is given by the subtraction of the minimumlight transmittance from the maximum light transmittance.

[0039] The antireflection substrate of the present invention is suitablefor optical components for semiconductor manufacturing apparatuses suchas various low-reflection lenses, substrates for low-reflectionphotomasks and substrates for low-reflection pellicles used in exposureto light in the ultraviolet and vacuum ultraviolet regions. Especially,for use as a substrate for a low-reflection pellicle (which is generallycalled “pellicle membrane” because it has been made of resin filmconventionally), the thickness is preferably from 1 μm to 2000 μm. Ifthe thickness is less than 1 μm, it is hard to handle, while if thethickness is more than 2000 μm, the light absorption by the substrate isremarkable. In view of optical uniformity, it is particularly preferredthat the thickness of the substrate is from 100 μm to 500 μm.

[0040] The antireflection substrate of the present invention may beproduced by forming an antireflection film having the above-mentionedstructure by means of a film forming machine such as an electron beanvapor deposition machine, an ion plating machine or a sputtering machineon each side or either side of the substrate. For example, when anelectron beam vapor deposition machine is used, the vacuum chamber setwith a substrate and vapor sources such as MgF₂ and SiO₂ is evacuated to1×10⁻³ Pa or below, and an antireflection film having theabove-mentioned structure is formed successively, while the thickness ismonitored with a film formation rate monitor of an optical type or aquartz oscillation type. Though vapor deposition of a fluoride layerdoes not require introduction of any particular reaction gas, anoxidizing gas such as oxygen at a partial pressure of about 0.1 Pa ispreferably introduced during vapor deposition of an oxide layer tofacilitate the oxidation. Heating of the substrate to about 300-400° C.before the film formation is also preferable in view of improvement inthe durability and the optical properties of the antireflection film.Antireflection films may be formed on both sides of the substrate byforming one on one side of the substrate, then flipping over thesubstrate, and forming another on the other side.

EXAMPLES

[0041] Now, the present invention will be described in more detail withreference to specific Examples. However, the present invention is by notmeans restricted to those specific Examples.

Examples 1 to 27 and Comparative Example

[0042] (Preparation of Substrates)

[0043] SiCl₄ was hydrolyzed in an oxyhydrogen flame by the conventionalsoot method, and the resulting fine SiO₂ particles were deposited on asubstrate to form a porous quartz glass body with a diameter of 400 mmand a length of 600 mm.

[0044] Then, a pressure vessel was loaded with the porous quartz glassbody, and the pressure was reduced to about 133 Pa and then returned toordinary pressure by introducing an inert gas (such as He). The pressurewas reduced again to about 133 Pa, and SiF₄ gas diluted with an inertgas (such as He) was introduced to raise the pressure nearly to ordinarypressure. After the introduction of the SiF₄ gas diluted with an inertgas (such as He) was stopped, the porous quartz glass body was allowedto stand still. Thus way, the porous quartz glass body was doped withfluorine.

[0045] The fluorine-doped porous quartz glass body was treated with heatin a controlled-atmosphere electric furnace (heated under a reducedpressure of 150 Pa or below, then maintained at 1000-1300° C. for apredetermined time, heated to 1450° C. and maintained at the sametemperature for 10 hours) to obtain a transparent quartz glass body(with a diameter of 200 mm and a length of 200 mm).

[0046] The glass body was ground and made into synthetic quartz glasssubstrates doped with 100 ppm of fluorine (with a diameter of 200 mm, athickness of 300 μm, an internal transmittance of at least 70% in thewavelength region of from 155 nm to 250 nm, an internal transmittance of90% at the wavelength of 157 nm, and an internal transmittance of atleast 99% at the wavelengths of 193 nm and 248 nm).

[0047] (Formation of Antireflection Films)

[0048] Antireflection films having the structures shown in Tables 1 and2 on the both sides of the fluorine-doped synthetic quartz glasssubstrates with a vapor deposition machine (which uses electron beams orresistance heat to heat a vapor source) to give antireflectionsubstrates having the structure shown in FIG. 1, 2 or 3.

[0049] The respective layers were formed by the following procedure.

[0050] A fluorine-doped synthetic quartz glass substrate and three vaporsources (MgF₂, SiO₂ and Al₂O₃) were set in the vacuum chamber of thevapor deposition machine, and the vacuum chamber was evacuated to 1×10⁻³Pa or below. Then, while the thickness was monitored with a filmformation rate monitor of an optical type, an intended layer wasdeposited by heating intended vapor sources (with electron beams in thecase of HgF₂ and with resistance heat in the cases of SiO₂ and Al₂O₃) onthe substrate, repeatedly in the cases of multilayer structure, to formantireflection film.

[0051] During vapor deposition of an oxide layer, an oxidizing gas(oxygen gas in these Examples) at a partial pressure of about 0.1 Pa wasintroduced to facilitate the oxidation. During film formation,substrates were heated to about 300° C. After one side of a substratewas subjected to vapor deposition, the substrate was flipped over, andthe opposite side was subjected to vapor deposition similarly to formantireflection films on both sides of the substrate.

[0052] (Evaluation)

[0053] Measurement of the Transmittance at the Antireflection CenterWavelength λ₀

[0054] The transmittances of the antireflection substrates obtained inExamples 1 to 27 at the antireflection center wavelength λ₀.

[0055] For measurement of the transmittances within the range of from150 to 190 nm, a vacuum ultraviolet spectrophotometer (Acton Research,VTM-502) was used. For measurement of the transmittances within therange of from 190 to 700 nm, a spectrophotometer (Varian, Cary 500) wasused.

[0056] Measurement of the Reflectance at the Antireflection CenterWavelength λ₀

[0057] The spectral reflectance of a single side of each antireflectionfilm obtained in Examples 1 to 27 was measured by the followingprocedure, and the reflectances at the antireflection center wavelengthλ₀ (the degrees of reflection from one side) were obtained from theresults.

[0058] For measurement of the spectral reflectance, the flip side of asubstrate was roughened by sand blasting so that only the lightreflected from the face side could be measured by scattering thereflected light from the flip side. For measurement within the range offrom 150 to 190 nm, a vacuum ultraviolet spectrophotometer (ActonResearch, VTM-502) was used. For measurement within the range of from190 to 700 nm, a spectrophotometer (Varian, Cary 500) was used.

[0059] The reflectance at the antireflection center wavelength of λ₀ wasalso measured with Comparative Example (a synthetic quartz glasssubstrate having no antireflection film).

[0060] Measurement of Thickness

[0061] The physical total thickness of the antireflection film (on oneside) of Example 19 was measured with DEKTAK.

[0062] Measurement of Double Refraction

[0063] The double refraction was measured in Example 19 with EXICOR350ATmanufactured by HINDS.

[0064] When the antireflection substrate of the present invention isused as an optical component for a semiconductor manufacturingapparatus, especially as the substrate for a low-reflection pellicle, itis preferred that the double refraction is at most 2 nm (particularly atmost 1.5 nm) in view of the adaptability to lithography.

[0065] Measurement of Surface Roughness (Ra)

[0066] An atomic force microscope (SPI3700, manufactured by Seiko) wasused for measurement of surface roughness Ra. A smaller Ra means lesslight scattering, less stray light generated from the exposure light andless displacement of the transferred pattern. When the antireflectionsubstrate of the present invention is used as the substrate for alow-reflection pellicle, the smaller the Ra, the easier it is toeliminate foreign matter by an air blow. From this viewpoint, the Ra ispreferably at most 1 nm.

[0067] Examples 1, 3 and 5 are embodiments wherein n₁d₁=0.25λ₀, andExamples of 2, 4 and 6 are embodiments wherein n₁d₁=(0.25+½)λ₀.

[0068] Examples 7 to 9, 11 to 13 and 15 to 17 are embodiments whereinn₁d₁ is almost 0.25λ₀, and 0.055λ₀≦n₂d₂≦0.45λ₀, and Examples 10, 14 and18 are embodiments wherein n₁d₁=(0.25+½)λ₀, and 0.055λ₀≦n₂d₂≦0.45λ₀.

[0069] Examples 19, 22 and 25 are embodiments wherein n₁d₁ and n₃d₃ areboth almost 0.25λ₀, and 0.16λ₀≦n₂d_(2≦)0.38λ₀. Examples 20, 23 and 26are embodiments wherein n₁d₁ and n₃d₃ are both almost 0.25λ₀, and0.64λ₀≦n₂d₂≦0.86λ₀.

[0070] Examples 21, 24 and 27 are embodiments wherein1.13λ₀≦n₂d₂≦1.35λ₀.

[0071] With respect to Examples 19, the physical total thickness of eachantireflection film (on one side) was 76 nm, the double refraction was0.2 nm, and Ra was 0.6 nm.

Example 28

[0072] The antireflection substrate obtained in Example 19 was checkedfor laser beam resistance. The laser beam exposure test was carried outwith a F₂ laser at 1 mJ/cm²/pulse, 300 Hz and a total radiation energyof 10000 J/cm². After the laser beam exposure test, there was notransmittance loss, no peeling of the antireflection film or no damage.

Example 29

[0073] The antireflection substrate obtained in Example 19 was processedinto a substrate for a low-reflection pellicle (120 mm×145 mm×300 μmthick) by means of a CO₂ laser. The resulting substrate for alow-reflection pellicle was attached to a pellicle frame to assemble alow-reflection pellicle.

[0074] After the surface of the low-reflection pellicle was swept withan air blow, the pellicle was checked for foreign matter by means ofPI-1000 (manufactured by QC OPTICS), and no foreign matter was notdetected.

[0075] The low-reflection pellicle was laid on a sliding XY stage, andmade slidable and the transmittance at the antireflection centerwavelength λ₀ (157 nm) was measured in the same manner as describedabove at intersections of grid lines drawn at 5 mm intervals. Thedifference between the maximum and the minimum of the transmittance was0.3%.

[0076] The low-reflection pellicle was mounted on a line and spacephotomask (with 0.15 μm intervals) with a pellicle mounter and used inphotolithography, and as a result, a good pattern was obtained.

[0077] Industrial Applicability

[0078] The antireflection substrate of the present invention controlsreflection in the ultraviolet and vacuum ultraviolet regions and hashigh transmittance by suppressing light loss resulting from surfacereflection and development of flare ghosts. Therefore, it is suitablyused for various low-reflection lenses, substrates of low-reflectionphotomasks and substrates of low-reflection pellicles (pelliclemembranes) used in exposure to ultraviolet and vacuum ultraviolet lightat wavelengths of from 150 nm to 200 nm in manufacture of semiconductorintegrated circuits.

[0079] It is also advantageous to facilitate the alignment of anexposure system using a He—Ne laser because the reflectance around 632.8nm can be reduced to 3.5% or lower by appropriately selecting the layerstructure and the refractive index and the physical thickness of eachlayer. TABLE 1 Anti- Degree of reflection reflection Transmittancecenter from one side at center wavelength Third layer Second layer Firstlayer at center wavelength Example λ₀ (n₃d₃/λ₀) (n₂d₂/λ₀) (n₁d₁/λ₀)wavelength (%) (%) 1 157 nm Nil Nil MgF₂ (0.25) 1.9 96.0 2 157 nm NilNil MgF₂ (0.75) 1.8 96.0 3 193 nm Nil Nil MgF₂ (0.25) 2.2 95.5 4 193 nmNil Nil MgF₂ (0.75) 2.2 95.5 5 248 nm Nil Nil MgF₂ (0.25) 2.1 95.5 6 248nm Nil Nil MgF₂ (0.75) 2.1 95.5 7 157 nm Nil Al₂O₃ (0.21) MgF₂ (0.23)1.1 87.6 8 157 nm Nil  Al₂O₃ (0.058) MgF₂ (0.23) 1.9 93.0 9 157 nm NilAl₂O₃ (0.45) MgF₂ (0.23) 1.8 76.2 10 157 nm Nil Al₂O₃ (0.21) MgF₂ (0.75)0.9 94.3 11 193 nm Nil Al₂O₃ (0.22) MgF₂ (0.25) 0.5 93.4 12 193 nm Nil Al₂O₃ (0.055) MgF₂ (0.25) 1.9 94.6 13 193 nm Nil Al₂O₃ (0.45) MgF₂(0.25) 2.1 85.6 14 193 nm Nil Al₂O₃ (0.22) MgF₂ (0.75) 0.5 93.4 15 248nm Nil Al₂O₃ (0.26) MgF₂ (0.25) 0.5 98.9 16 248 nm Nil  Al₂O₃ (0.055)MgF₂ (0.25) 2.1 95.6

[0080] TABLE 2 Anti- Degree of reflection reflection Transmittancecenter from one side at center wavelength Third layer Second layer Firstlayer at center wavelength Example λ₀ (n₃d₃/λ₀) (n₂d₂/λ₀) (n₁d₁/λ₀)wavelength (%) (%) 17 248 nm Nil Al₂O₃ (0.45) MgF₂ (0.25) 2.0 95.8 18248 nm Nil Al₂O₃ (0.26) MgF₂ (0.75) 0.5 98.9 19 157 nm MgF₂ (0.24) SiO₂(0.27) MgF₂ (0.23) 0.4 98.9 20 157 nm MgF₂ (0.23) SiO₂ (0.80) MgF₂(0.23) 0.5 98.8 21 157 nm MgF₂ (0.22) SiO₂ (1.32) MgF₂ (0.21) 0.5 98.922 193 nm MgF₂ (0.25) SiO₂ (0.25) MgF₂ (0.25) 0.6 98.6 23 193 nm MgF₂(0.25) SiO₂ (0.75) MgF₂ (0.25) 0.7 98.6 24 193 nm MgF₂ (0.25) SiO₂(1.25) MgF₂ (0.25) 0.6 98.6 25 248 nm MgF₂ (0.25) SiO₂ (0.25) MgF₂(0.25) 0.8 98.2 26 248 nm MgF₂ (0.25) SiO₂ (0.75) MgF₂ (0.25) 0.8 98.227 248 nm MgF₂ (0.25) SiO₂ (1.25) MgF₂ (0.25) 0.9 98.2 Comparative 157nm Nil Nil Nil 87.7 Example 193 nm Nil Nil Nil 90.8 248 nm Nil Nil Nil92.1

[0081] The entire disclosure of Japanese Patent Application No.2000-325634 filed on May 7, 2000 including specification, claims,drawings and summary are incorporated herein by reference in itsentirety.

[0082] The entire disclosures of JP11-315376, filed Nov. 5, 1999, andPCT/JP00/07724, filed Nov. 2, 2000, are incorporated herein byreference.

What is claimed is:
 1. An ultraviolet and vacuum ultravioletantireflection substrate comprising a substrate which is transparent toultraviolet and vacuum ultraviolet rays in the wavelength region from155 nm to 200 nm and a monolayer antireflection film formed on at leastone side of the substrate, wherein the center wavelength λ₀ of thewavelength region of ultraviolet or vacuum ultraviolet light which needsantireflection, the refractive index n_(s) of the substrate at thewavelength of λ₀, the refractive index n₁ of the antireflection film atthe wavelength of λ₀ and the physical thickness d₁ of the antireflectionfilm satisfy the conditions that n₁<n_(s), and that n₁d₁ is almost(¼+m/2)λ₀ (wherein m is an integer of at least 0).
 2. An ultraviolet andvacuum ultraviolet antireflection substrate comprising a substrate whichis transparent to ultraviolet and vacuum ultraviolet rays in thewavelength region from 155 nm to 200 nm and a bilayer antireflectionfilm comprising a second layer and a first layer formed on at least oneside of the substrate in this order from the substrate side, wherein thecenter wavelength λ₀ of the wavelength region of ultraviolet or vacuumultraviolet light which needs antireflection, the refractive index n_(s)of the substrate at the wavelength of λ₀, the refractive index n₂ of thesecond layer at the wavelength of λ₀, the physical thickness d₂ of thesecond layer, the refractive index n₁ of the first layer at thewavelength of λ₀, and the physical thickness d₁ of the first layersatisfy the conditions that n₁<n_(s)<n₂, that n₁d₁ is almost (¼+m/2)λ₀(wherein m is an integer of at least 0), and that 0.05λ₀≦n₂d₂≦0.50λ₀. 3.An ultraviolet and vacuum ultraviolet antireflection substratecomprising a substrate which is transparent to ultraviolet and vacuumultraviolet rays in the wavelength region from 155 nm to 200 nm and atrilayer antireflection film comprising a third layer, a second layerand a first layer formed on at least one side of the substrate in thisorder from the substrate side, wherein the center wavelength λ₀ of thewavelength region of ultraviolet or vacuum ultraviolet light which needsantireflection, the refractive index n_(s) of the substrate at thewavelength of λ₀, the refractive index n₃ of the third layer at thewavelength of λ₀, the physical thickness d₃ of the third layer, therefractive index n₂ of the second layer at the wavelength of λ₀, thephysical thickness d₂ of the second layer, the refractive index n₁ ofthe first layer at the wavelength of λ₀, and the physical thickness d₁of the first layer satisfy the following conditions (1) to (4): n ₁ , n₃ <n _(s) and n ₁ , n ₃ <n ₂,  (1)0<n ₁ d ₁≦0.47λ₀,  (2)0.14λ₀ ≦n ₃ d₃≦0.33λ₀,  (3) and 0.16λ₀ ≦n ₂ d ₂≦0.38λ₀,0.64λ ₀ ≦n ₂ d ₂≦0.86λ₀,or1.13λ₀ ≦n ₂ d ₂≦1.35λ₀.
 4. The ultraviolet and vacuum ultravioletantireflection substrate according to claims 1, wherein the totalthickness of the antireflection film is at most 150 nm.
 5. Theultraviolet and vacuum ultraviolet antireflection substrate according toclaims 1, wherein the substrate is made of a synthetic quartz glassdoped with at least 1 ppm of fluorine.
 6. The ultraviolet and vacuumultraviolet antireflection substrate according to claims 1, wherein thethickness of the substrate is from 100 μm to 500 μm.
 7. The ultravioletand vacuum ultraviolet antireflection substrate according to claim 5,wherein the layer in the antireflection film which is in contact withthe substrate is made of a fluoride.
 8. The ultraviolet and vacuumultraviolet antireflection substrate according to claims 1, wherein thecenter wavelength λ₀ is from 150 nm to 200 nm.
 9. The ultraviolet andvacuum ultraviolet antireflection substrate according to claim 8,wherein the center wavelength λ₀ is 157 nm or 193 nm.
 10. Theultraviolet and vacuum ultraviolet antireflection substrate according toclaims 1, wherein the reflectance around the wavelength of 632.8 nm isat most 3.5%.
 11. The ultraviolet and vacuum ultraviolet antireflectionsubstrate according to claims 1, wherein the difference between themaximum and the minimum of the transmission of light at the centerwavelength λ₀ is at most 1%.
 12. An optical component for asemiconductor manufacturing apparatus, which is the ultraviolet andvacuum ultraviolet antireflection substrate according to claims
 1. 13. Asubstrate for a low-reflection pellicle, which is the ultraviolet andvacuum ultraviolet antireflection substrate according to claims 1.